Novel polypeptide

ABSTRACT

A screening tool and a screening method for a therapeutic agent for type II diabetes, particularly an agent for alleviating insulin resistance are disclosed. A novel polypeptide, a polynucleotide, a vector, a promoter, and a transformant which are useful in the screening tool and the screening method, are also disclosed.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Divisional of U.S. application Ser. No. 10/491,277 filed Mar. 31, 2004 (now allowed); which is a 371 of PCT/JP03/01788, filed Feb. 19, 2003; the entire disclosure of each of these applications is incorporated herein by reference.

TECHNICAL FIELD

This invention relates to a novel polypeptide useful when screening a therapeutic agent for type II diabetes, particularly an agent for alleviating insulin resistance, and to a screening tool and a screening method for a therapeutic agent for type II diabetes, particularly an agent for alleviating insulin resistance.

BACKGROUND ART

The number of people diagnosed as diabetic is increasing, due to insufficient exercise or a westernization of life style, such as a habit of eating a high fat diet. Diabetes which more than 90% of patients are suffering from are type II diabetes, characterized by a deficiency of insulin action caused by an increase of insulin resistance or a decrease of insulin secretion.

In a healthy person, when the blood glucose level is increased by food ingestion, insulin secreted from the pancreas is rapidly increased. In response to the resultant insulin concentration, an action of decreasing the glucose release in the liver and an action of increasing the glucose uptake in skeletal muscles and adipose tissues occur, and thus the blood glucose level is decreased and returns to the normal level. However, in a patient suffering from type II diabetes exhibiting an insulin resistance, due to a low sensibility to insulin in tissues, a decrease of the glucose release in the liver or an increase of the glucose uptake in muscles and adipose tissues in response to insulin is not sufficient, and thus abnormal changes in the blood glucose level, such as postprandial hyperglycemia or fasting hyperglycemia, is observed. After the developing of diabetes, the diabetes progresses without subjective symptoms for a long time. Because complications, such as diabetic retinopathy, diabetic nephropathy, or neuropathy, supervene in severe diabetes, it is very important to prevent or treat diabetes at an early stage.

As therapeutic agents for diabetes capable of alleviating insulin resistance, biguanides, which increase the action of inhibiting glucose release in the liver as the main effect, or thiazoline derivatives, which decrease the insulin resistance in the liver, fat, and/or skeletal muscles as the main effect, are clinically used. However, a cautious administration is required due to complications, side effects, or the like, and thus a more efficient agent exhibiting no side effects is desired for alleviating insulin resistance (non-patent reference 1).

The decreased insulin action to glucose metabolism is commonly observed in type II diabetes, and closely involved in abnormal glucose metabolism in the whole body. Therefore, a pathological clarification of type II diabetes and development of therapeutic agents therefor must clarify a mechanism of promoting glucose transport by insulin (non-patent reference 2). In other words, a factor which inhibits the glucose transport mechanism is probably involved in diabetes.

Insulin and insulin-like growth factor I (IGF-I) are peptide hormones belonging to the same family, and are highly similar in structure and functions. Further, the insulin receptor and IGF-I receptor are homologous molecules belonging to a tyrosine kinase-type receptor family, and each native ligand thereof exhibits a cross-reactivity for the other receptor (non-patent reference 3). It is known that a signal transduction is promoted by binding insulin or IGF-1 with the receptor thereof, and that a glucose uptake from extracellular fluid causes an action of decreasing blood glucose (non-patent reference 4). IGF-I alone is not stable in blood, and more than 90% thereof forms complexes with insulin-like growth factor binding protein (IGFBP), to maintain stability, and thus it is considered that the existence of IGFBP is important from the viewpoint of tissue delivery or control of the action (non-patent reference 5). Many reports on the relationship between diabetes and IGFBP have been made, and it is known, for example, that IGFBP-3 and IGFBP-5 are decreased in the blood of patients suffering from type I/II diabetes (non-patent reference 6), that an N-terminus undigested product (18 kDa) of IGFBP-3 is increased in the urine of patients suffering from type I diabetes (non-patent reference 7), that when streptozotocin, which specifically destroys pancreatic β cells and can cause diabetes by experimentally administering it to an animal, is administered to rat to induce diabetes, IGFBP-3 is expressed together with IGFBP-5 in renal glomeruli (non-patent reference 8), that a positive correlation between an activity of digesting IGFBP-3 in the urine of patients suffering from type II diabetes with diabetic nephropathy and an amount of albumin leaked into the urine of patients suffering from diabetic nephropathy is observed (non-patent reference 9), that a polymorphism of causes of type I diabetes exists near the IGFBP-2 and IGFBP-5 genes (non-patent reference 10), and that when IGFBP-3 is digested by protease, the affinity thereof for IGF-I is decreased and the affinity of the digested N-terminus fragment for insulin is increased (non-patent reference 11 and non-patent reference 12).

As described above, it is considered that an effective method for treating diabetes (alleviating insulin resistance) can be also provided by inhibiting IGFBP digestion.

In this connection, the deduced amino acid sequence of human ADAM8 is known, and it is suggested that human ADAM8 is metalloprotease and is involved in tumors and platelet aggregation (patent reference 1, patent reference 2, non-patent reference 13, non-patent reference 14, and non-patent reference 15). However, a relationship between human ADAM8 and diabetes is not suggested.

-   (non-patent reference 1) Ryuzo Kawamori et al., “Tonyoubyou 2001     Karada no Kagaku, zoukan (supplement)”, Nippon-Hyoron-sha, 2001,     p.86-108 -   (non-patent reference 2) Oka, “Saishin Igaku (The Medical Frontline     )”, 2002, p.41-46 -   (non-patent reference 3) Miyazono et al., “Saitokain & zoshoku Inshi     (Cytokines and growth factors)”, YODOSHA, 104-109, 1998 -   (non-patent reference 4) Kadowaki et al., “Medical terms libraly,     diabetes”, YODOSHA, 52-53, 1995 -   (non-patent reference 5) Yamanaka et al., “Horumon to Rinsho     (CLINCAL ENDOCRINOLOGY)”, 29-38, 1998 -   (non-patent reference 6) J. Endocrinol., 159, 297-306, 1998 -   (non-patent reference 7) Clinical Endocrinology, 51, 587-596, 1999 -   (non-patent reference 8) Am. J. Kidney. diseases, 1000-1010, -   (non-patent reference 9) J. Clin. Endo. Metab., 85, 1163-1169, 2000 -   (non-patent reference 10) Science, 272, 1811-1813, 1996 -   (non-patent reference 11) Yamanaka Y. et al., J. Biol. Chem., 272,     30729-30734, 1997 -   (non-patent reference 12) Peter V. et al., J. Clin. Endocrinol.     Metab., 83, 1392-1395,1998 -   (non-patent reference 13) SWISSPROT P78325 AD08 HUMAN(1997.11.1)     available on the internet at     kr.expasy.org/cgi-bin/niceprot.pl?P78325 -   (non-patent reference 14) NCBI D265791 Homo sapiens mRNA (1999.2.6)     available on the internet at     ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=nucleotid     e&list_uids=1864004&dopt=GenBank -   (non-patent reference 15) Genomics 1997 Apr. 1 41, 56 CD156 -   (human ADAM8) -   (patent reference 1) WO01/09189 -   (patent reference 2) WO01/53486

DISCLOSURE OF INVENTION

The present inventors conducted intensive studies into the provision of a screening system for obtaining a novel agent for alleviating insulin resistance and, as a result, found a gene of which the expression was increased in a diabetes model mouse and obtained the gene (mouse MD8 gene), a human ortholog gene (human MD8 gene), and a promoter of the human MD8 gene. Further, the present inventors found that an overexpression of the mouse MD8 or human MD8 in adipocytes inhibits glucose uptake by an insulin stimulation, and that human MD8 is a novel protease having an activity of digesting IGFBP. In this connection, it is considered that insulin resistance is increased by digesting IGFBP. On the basis of these findings, the present inventors clarified that MD8 and the promoter thereof can be used as a tool useful when screening a novel therapeutic agent for diabetes (particularly an agent for alleviating insulin resistance), and provided a novel screening tool and screening method for a novel therapeutic agent for diabetes (particularly an agent for alleviating insulin resistance) and a novel method for manufacturing a novel pharmaceutical composition for treating diabetes (particularly an agent for alleviating insulin resistance), and thus the present invention was completed.

The present invention relates to:

-   [1] a screening tool for a therapeutic agent for diabetes, wherein     the tool is -   (1) a polypeptide consisting of the amino acid sequence of SEQ ID     NO: 2 or SEQ ID NO: 14, -   (2) a polypeptide exhibiting an activity of inhibiting glucose     uptake into an adipocyte by an insulin stimulation, and comprising     an amino acid sequence in which 1 to 10 amino acids are deleted,     substituted, and/or inserted in the amino acid sequence of SEQ ID     NO: 2 or SEQ ID NO: 14, -   (3) a polypeptide exhibiting an activity of inhibiting glucose     uptake into an adipocyte by an insulin stimulation, and comprising     the amino acid sequence of SEQ ID NO: 2 or SEQ ID NO: 14, or -   (4) a polypeptide exhibiting an activity of inhibiting glucose     uptake into an adipocyte by an insulin stimulation, and consisting     of an amino acid sequence having an 80% or more homology with that     of SEQ ID NO: 2 or SEQ ID NO: 14; -   [2] the screening tool for a therapeutic agent for diabetes of [1],     wherein the tool is (1) a polypeptide consisting of the amino acid     sequence of SEQ ID NO: 2 or SEQ ID NO: 14; -   [3] a screening tool for a therapeutic agent for diabetes, wherein     the tool is a cell expressing the polypeptide of [1] or [2]; -   [4] the screening tool for a therapeutic agent for diabetes of [3],     wherein the cell is a transformant; -   [5] a screening tool for a therapeutic agent for diabetes, wherein     the tool is -   (1) a polynucleotide consisting of the base sequence consisting of     the 34th to 2014th bases in the base sequence of SEQ ID NO: 20, -   (2) a polynucleotide exhibiting a promoter activity of the     polypeptide of [1] or [2], and comprising a base sequence in which     one or more bases are substituted, deleted, and/or inserted at 1 to     10 positions in the base sequence consisting of the 34th to 2014th     bases in the base sequence of SEQ ID NO: 20, -   (3) a polynucleotide exhibiting a promoter activity of the     polypeptide of [1] or [2], and comprising at least a part of the     base sequence consisting of the 34th to 2014th bases in the base     sequence of SEQ ID NO: 20, or -   (4) a polynucleotide exhibiting a promoter activity of the     polypeptide of [1] or [2], and hybridizing under stringent     conditions to a polynucleotide consisting of the base sequence     consisting of the 34th to 2014th bases in the base sequence of SEQ     ID NO: 20; -   [6] the screening tool for a therapeutic agent for diabetes of [5],     wherein the polypeptide exhibits a promoter activity of the     polypeptide of [1] or [2], and comprises the base sequence     consisting of the 34th to 2014th bases in the base sequence of SEQ     ID NO: 20; -   [7] a screening tool for a therapeutic agent for diabetes, wherein     the tool is a cell comprising the polynucleotide of [5] or [6]; -   [8] the screening tool for a therapeutic agent for diabetes of [7],     wherein the cell is a transformant; -   [9] the screening tool or [1] to [8], wherein the therapeutic agent     for diabetes is an agent for alleviating insulin resistance; -   [10] a method for analyzing whether or not a substance to be tested     is an inhibitor of the polypeptide of [1] or [2], comprising the     steps of: -   bringing a cell expressing the polypeptide of [1] or [2] into     contact with the substance to be tested, and -   analyzing an amount of glucose uptake by an insulin stimulation; -   [11] a method for screening an inhibitor of the polypeptide of [1]     or [2], comprising the steps of: -   analyzing a substance to be tested by the method of [10], and -   selecting an inhibitor; -   [12] a method for screening a therapeutic agent for diabetes,     comprising the steps of: -   analyzing a substance to be tested by the method of [10], and -   selecting an inhibitor; -   [13] a method for analyzing whether or not a substance to be tested     inhibits a promoter activity of the polynucleotide of [5]or [6],     comprising the steps of: -   (1) bringing the cell of [7] or [8] into contact with the substance     to be tested, and -   (2) analyzing the promoter activity; -   [14] a method for screening a substance which inhibits an expression     of the polypeptide of [1] or [2], comprising the steps of: -   analyzing a substance to be tested by the method of [13], and -   selecting a substance which inhibits the promoter; -   [15] a method for screening a therapeutic agent for diabetes,     comprising the steps of: -   analyzing a substance to be tested by the method of [13], and -   selecting a substance which inhibits the promoter activity; -   [16] a process for manufacturing a pharmaceutical composition for     treating diabetes, comprising the steps of: -   analyzing a substance to be tested by the method of [10] or [13],     and -   preparing a medicament containing the substance; -   [17] a polypeptide exhibiting an activity of inhibiting glucose     uptake into an adipocyte by an insulin stimulation, -   and comprising the amino acid sequence of SEQ ID NO: 2; -   [18] a polypeptide consisting of the amino acid sequence of SEQ ID     NO: 2; -   [19] a polynucleotide encoding the polypeptide of [17] or [18]; -   [20]a vector expressibly comprising the polynucleotide of [19]; -   [21] a transformant comprising the polynucleotide of [19]; -   [22] (1) a polynucleotide consisting of the base sequence consisting     of the 34th to 2014th bases in the base sequence of SEQ ID NO: 20, -   (2) a polynucleotide exhibiting a promoter activity of the     polypeptide of [1] or [2], and comprising a base sequence in which     one or more bases are substituted, deleted, and/or inserted at 1 to     10 positions in the base sequence consisting of the 34th to 2014th     bases in the base sequence of SEQ ID NO: 20, -   (3) a polynucleotide exhibiting a promoter activity of the     polypeptide of [1] or [2], and comprising at least a part of the     base sequence consisting of the 34th to 2014th bases in the base     sequence of SEQ ID NO: 20, or -   (4) a polynucleotide exhibiting a promoter activity of the     polypeptide of [1] or [2], and hybridizing under stringent     conditions to a polynucleotide consisting of the base sequence     consisting of the 34th to 2014th bases in the base sequence of SEQ     ID NO: 20; -   [23] the polynucleotide of [22], exhibiting a promoter activity of     the polypeptide of [1] or [2], and comprising the base sequence     consisting of the 34th to 2014th bases in the base sequence of SEQ     ID NO: 20; -   [24] a transformant comprising the polynucleotide of [22] or [23]; -   [25] a method for producing the polypeptide of [17] or [18],     comprising the step of: -   culturing the transformant of [21] ; and -   [26] a probe which hybridizes to the polynucleotide of [19] under     stringent conditions[19].

The present invention includes use of the polypeptide of [1] or [2], the cell of [3], [4], [7], or [8], and the polynucleotide of [5] or [6] for screening a therapeutic agent for diabetes. As the “therapeutic agent for diabetes”, an agent for alleviating insulin resistance is preferable. The “therapeutic agent for diabetes” or “pharmaceutical composition for treating diabetes” includes both an agent or pharmaceutical composition used for treating a patient suffering from diabetes and that preventively used for a subject exhibiting signs of diabetes.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a graph showing amounts of glucose uptake by an insulin stimulation in differentiated adipocytes infected with the mMD8 virus or control virus.

FIG. 2 is a graph showing amounts of glucose uptake by an insulin stimulation in differentiated adipocytes infected with the MD8 virus or control virus.

FIG. 3 is a drawing showing the results of electrophoresis which shows that an activity of digesting recombinant IGFBP-3 and IGFBP-5 by the MD8S protein obtained in Example 10 was inhibited by the compound A.

FIG. 4 is a graph showing the results of a luciferase assay using the MD8 promoter region.

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention will be explained in detail hereinafter.

Genetic recombination techniques may be performed in accordance with known methods (for example, “Molecular Cloning-A Laboratory Manual”, Cold Spring Harbor Laboratory, N.Y., 1989; or WO01/34785).

1. Screening Tool of the Present Invention

The screening tool of the present invention for a therapeutic agent for diabetes, particularly an agent for alleviating insulin resistance, includes a polypeptide-type screening tool, cell-type screening tool, and promoter-type screening tool.

(1) Polypeptide-type Screening Tool

As the polypeptide which may be used as the polypeptide-type screening tool of the present invention, there may be mentioned, for example,

-   (i) a polypeptide consisting of the amino acid sequence of SEQ ID     NO: 2 or SEQ ID NO: 14; -   (ii) (a) a polypeptide exhibiting an activity of inhibiting glucose     uptake into an adipocyte by an insulin stimulation, and comprising     an amino acid sequence in which 1 to 10 amino acids are deleted,     substituted, and/or inserted in the amino acid sequence of SEQ ID     NO: 2 or SEQ ID NO: 14; or (b) a polypeptide exhibiting an activity     of inhibiting glucose uptake into an adipocyte by an insulin     stimulation, and comprising the amino acid sequence of SEQ ID NO: 2     or SEQ ID NO: 14 (hereinafter referred to as a variation     functionally equivalent); or -   (iii) a polypeptide exhibiting an activity of inhibiting glucose     uptake into an adipocyte by an insulin stimulation, and consisting     of an amino acid sequence having a 80% or more homology with that of     SEQ ID NO: 2 or SEQ ID NO: 14 (hereinafter referred to as a     homologous polypeptide).

Hereinafter, the polypeptides which may be used as the polypeptide-type screening tool of the present invention are collectively referred to as polypeptides for a screening tool.

The “polypeptide consisting of the amino acid sequence of SEQ ID NO: 2” (hereinafter sometimes referred to as MD8 protein) and the “polypeptide consisting of the amino acid sequence of SEQ ID NO: 14” (hereinafter sometimes referred to as mMD8 protein), which are polypeptides of the present invention for a screening tool, are a novel human polypeptide consisting of 824 amino acid residues and a mouse polypeptide consisting of 825 amino acid residues, respectively. The MD8 protein and MMD8 protein are metalloproteases having a zinc-coordinated consensus sequence (HExxH: SEQ ID NO: 15).

The polypeptide consisting of the amino acid sequence of SEQ ID NO: 2 or 14 exhibits an activity of inhibiting glucose uptake into an adipocyte by an insulin stimulation.

“To exhibit an activity of inhibiting glucose uptake into an adipocyte by an insulin stimulation” as used herein means, when an adipocyte expressing a polypeptide as a target and an adipocyte without expressing the polypeptide are independently stimulated by insulin and then amounts of glucose uptake in the adipocytes are compared, to decrease the amount of glucose uptake in the adipocyte expressing the polypeptide. Comparison of the amounts of glucose uptake by an insulin stimulation can be performed, for example, in. accordance with methods described in Examples 4-7. As the degree of the decrease of glucose uptake, 20% or more is preferable, 50% or more is more preferable, and 80% or more is most preferable.

As the variation functionally equivalent which may be used as the polypeptide-type screening tool of the present invention,

-   (a) a polypeptide exhibiting an activity of inhibiting glucose     uptake into an adipocyte by an insulin stimulation, and consisting     of an amino acid sequence in which 1 to 10 (preferably 1 to 7, more     preferably 1 to 5) amino acids in total are deleted, substituted,     inserted, and/or added at one or plural positions in the amino acid     sequence of SEQ ID NO: 2 or SEQ ID NO: 14; or -   (b) a polypeptide exhibiting an activity of inhibiting glucose     uptake into an adipocyte by an insulin stimulation, and comprising     the amino acid sequence of SEQ ID NO: 2 or SEQ ID NO: 14 are     preferable.

The polypeptides exhibiting an activity of inhibiting glucose uptake into an adipocyte by an insulin stimulation, and comprising the amino acid sequence of SEQ ID NO: 2 or SEQ ID NO: 14 include, for example, a polypeptide in which an appropriate marker sequence or the like is added to the N-terminus and/or the C-terminus of the polypeptide consisting of the amino acid sequence of SEQ ID NO: 2 or SEQ ID NO: 14 (i.e., a fusion polypeptide), so long as the fusion polypeptide exhibits an activity of inhibiting glucose uptake into an adipocyte by an insulin stimulation.

As the marker sequence, for example, a sequence for easily carrying out a confirmation of polypeptide expression, confirmation of intracellular localization thereof, purification thereof, or the like may be used. As the sequence, there may be mentioned, for example, the FLAG epitope, the hexa-histidine tag, the hemagglutinin tag, the myc epitope, or the like.

The homologous polypeptide which may be used as the polypeptide-type screening tool of the present invention may consist of an amino acid sequence having preferably a 90% or more homology, more preferably a 95% or more homology, still further preferably a 98% or more homology, most preferably a 99% or more homology, with respect to the amino acid sequence of SEQ ID NO: 2 or SEQ ID NO: 14.

The term “homology” as used herein means a value obtained by a BLAST (Basic local alignment search tool; Altschul, S. F. et al., J. Mol. Biol., 215, 403-410, 1990). The homology in the amino acid sequence may be calculated by a BLAST search algorithm. More particularly, it may be calculated using a bl2seq program (Tatiana A. Tatusova and Thomas L. Madden, FEMS Microbiol. Lett., 174, 247-250, 1999) in a BLAST package (sgi32 bit edition, version 2.0.12; obtained from NCBI) in accordance with a default parameter. As a pairwise alignment parameter, a program “blastp” is used. Further, “0” as a Gap insertion cost value, “0” as a Gap elongation cost value, “SEG” as a filter for a Query sequence, and “BLOSUM62” as a Matrix are used, respectively.

The present invention includes “a polypeptide exhibiting an activity of inhibiting glucose uptake into an adipocyte by an insulin stimulation, and consisting of a partial fragment of the polypeptide consisting of the amino acid sequence of SEQ ID NO: 2 or SEQ ID NO: 14”.

(2) Cell-type Screening Tool

The cell which may be used as the cell-type screening tool of the present invention (hereinafter referred to as a cell for a screening tool) is not particularly limited, so long as it expresses the polypeptide for a screening tool when using as the cell-type screening tool. The cell for a screening tool may be a transformant in which the polypeptide for a screening tool is artificially expressed, or a naturally occurring cell which is known to express the polypeptide for a screening tool, or a cell strain thereof. A transformant obtained by transformation with the polypeptide for a screening tool is preferable. As a most preferred cell-type screening tool, there may be mentioned, for example,

-   (i) a transformant expressing the polypeptide consisting of the     amino acid sequence of SEQ ID NO: 2 or SEQ ID NO: 14; -   (ii) a transformant expressing the variation functionally     equivalent; and -   (iii) a transformant expressing the homologous polypeptide.     (3) Promoter-type Screening Tool

The polypeptide which may be used as the promoter-type screening tool of the present invention (hereinafter referred to as a promoter of the present invention) is not particularly limited, so long as it is

-   (1) a polynucleotide consisting of the base sequence consisting of     the 34th to 2014th bases in the base sequence of SEQ ID NO: 20, -   (2) a polynucleotide exhibiting a promoter activity of the     polypeptide for a screening tool, and comprising a base sequence in     which one or more bases are substituted, deleted, and/or inserted at     1 to 10 positions in the base sequence consisting of the 34th to     2014th bases-in the base sequence of SEQ ID NO: 20, -   (3) a polynucleotide exhibiting a promoter activity of the     polypeptide for a screening tool, and comprising at least a part of     the base sequence consisting of the 34th to 2014th bases in the base     sequence of SEQ ID NO: 20, or -   (4) a polynucleotide exhibiting a promoter activity of the     polypeptide for a screening tool, and hybridizing under stringent     conditions to a polynucleotide consisting of the base sequence     consisting of the 34th to 2014th bases in the base sequence of SEQ     ID NO: 20. As the promoter of the present invention, for example, -   (i) a polynucleotide consisting of the base sequence consisting of     the 34th to 2014th bases in the base sequence of SEQ ID NO: 20; -   (ii) a polynucleotide exhibiting a promoter activity of the     polypeptide for a screening tool, and comprising a polynucleotide     consisting of the 34th to 2014th bases in the base sequence of SEQ     ID NO: 20, or -   (iii) a polynucleotide exhibiting a promoter activity of the     polypeptide for a screening tool, and comprising a base sequence in     which one or more (preferably 1 to 10 in total, more preferably 1 to     5, most preferably 1 to 3) bases are substituted, deleted, and/or     inserted at 1 to 10 positions in the base sequence consisting of the     34th to 2014th bases in the-base sequence of SEQ ID NO: 20     is preferable, and a polynucleotide exhibiting a promoter activity     of the polypeptide of the present invention described below is more     preferable.

The term “stringent conditions” as used herein means conditions in which non-specific hybridization does not occur, more particularly, conditions in which a 0.1×SSC (Saline-sodium citrate buffer) solution containing 0.1% sodium dodecyl sulfate (SDS) is used and the temperature is 65° C.

The cell which may be used as the promoter-type screening tool of the present invention (hereinafter referred to as a cell expressing a promoter of the present invention) is not particularly limited, so long as it is a cell expressing a promoter activity. As the cell expressing a promoter of the present invention, a cell transformed with the promoter of the present invention is preferable.

The term “promoter activity” as used herein means an activity of regulating an amount of an mRNA transcribed from a gene located downstream of the promoter. “To exhibit a promoter activity of the polypeptide for a screening tool (or polypeptide of the present invention)” as used herein means to be able to confirm a promoter activity of the polypeptide for a screening tool (or polypeptide of the present invention) by the method described in Example 12.

A substance which inhibits an expression of the polypeptide for a screening tool of the present invention or the polypeptide of the present invention can be screened, by using the promoter of the present invention and analyzing whether or not a substance to be tested inhibit an activity of the promoter of the present invention. The polypeptide for a screening tool of the present invention or the polypeptide of the present invention inhibits glucose uptake by insulin. Therefore, a substance which inhibits the promoter activity, i.e., a substance which inhibits the polypeptide expression, alleviates the inhibition of glucose uptake by insulin (i.e., insulin resistance), and is useful as an active ingredient of a therapeutic agent for treating diabetes (particularly an agent for alleviating insulin resistance). The promoter-type screening tool of the present invention may be used as a screening tool for a therapeutic agent for treating diabetes (particularly an agent for alleviating insulin resistance).

2. Polypeptide and Polynucleotide of the Present Invention

The polypeptide of the present invention includes the polypeptide consisting of the amino acid sequence of SEQ ID NO: 2, or the polypeptide exhibiting an activity of inhibiting glucose uptake into an adipocyte by an insulin stimulation, and comprising the amino acid sequence of SEQ ID NO: 2.

The polynucleotide of the present invention is not particularly limited, so long as it encodes the polypeptide of the present invention. As the polynucleotide of the present invention, a polynucleotide which encodes “the polypeptide consisting of the amino acid sequence of SEQ ID NO: 2”, more particularly a polynucleotide consisting of the base sequence consisting of the 1st to 2472nd bases in the base sequence of SEQ ID NO: 1, is preferable. In this connection, the term “polynucleotide” as used herein includes both DNA and RNA.

3. Method for Producing the Polypeptide-type or Cell-type Screening Tool, Polypeptide, and Polynucleotide of the Present Invention

The method for producing the polynucleotide of the present invention and the polynucleotide which encodes the polypeptide for a screening tool (hereinafter referred to as a polynucleotide for a screening tool) is not particularly limited. As the process, there may be mentioned, for example, (a) a method utilizing a polymerase chain reaction (PCR), (b) a method utilizing conventional genetic engineering techniques (i.e., a method for selecting a transformant containing the desired CDNA from strains transformed with a cDNA library), (c) a chemical synthesis method, or the like. These methods will be explained in this order hereinafter.

In the method using PCR [the above method (a)], the polynucleotide of the present invention or the polynucleotide for a screening tool may be produced, for example, by the following procedure.

mRNA is extracted from cells (for example, human or mouse cells) or tissue capable of producing the polypeptide of the present invention or the polypeptide for a screening tool. A primer set consisting of a pair of primers, between which full-length mRNA corresponding to the polypeptide or a partial region of the mRNA is located, is synthesized on the basis of the base sequence of a polynucleotide encoding the polynucleotide. Full-length cDNA encoding the polypeptide of the present invention or the polypeptide for a screening tool, or a part of the full-length cDNA may be obtained, by adjusting reaction conditions (for example, denaturation temperature, conditions for adding a denaturing agent, or the like) and performing a reverse transcriptase-polymerase chain reaction (RT-PCR).

Alternatively, full-length cDNA encoding the polypeptide or a part of the cDNA may be obtained, by performing PCR using, as a template, cDNA prepared using reverse transcriptase and mRNA derived from cells (for example, human or mouse cells) or tissue capable of producing the polypeptide, or commercially available cDNA derived from human or mouse cells or tissue.

The polypeptide may be manufactured by inserting the resulting full-length cDNA or a part thereof into an appropriate expression vector and expressing it in host cells.

In the method using conventional genetic engineering techniques [the above method (b)], the polynucleotide of the present invention or the polynucleotide for a screening tool may be produced, for example, by the following procedure.

First, single-stranded cDNA is synthesized by using reverse transcriptase from mRNA prepared by the above-mentioned PCR method as a template, and then double-stranded cDNA is synthesized from the single-stranded cDNA. Next, a recombinant plasmid comprising the double-stranded cDNA is prepared and introduced into Escherichia coli, such as a DH5α strain, HB101 strain, or JM109 strain, thereby transforming the strain. A transformant is selected using a drug resistance against, for example, tetracycline, ampicillin, or kanamycin as a marker.

As a method for selecting a transformant containing the desired cDNA from the resulting transformants, for example, (1) a screening method utilizing hybridization with a synthetic oligonucleotide probe, or (2) a screening method utilizing hybridization with a probe prepared by PCR, may be used.

The polynucleotide of the present invention or the polynucleotide for a screening tool may be obtained from the resulting transformant of interest in accordance with known methods, for example, by separating a fraction corresponding to plasmid DNA from the cells and cutting out the cDNA region from the plasmid DNA.

In the method using a chemical synthesis method [the above method (c)], the polynucleotide of the present invention or the polynucleotide for a-screening tool may be produced, for example, by binding DNA fragments produced by a chemical synthesis method. Each DNA can be synthesized using a DNA synthesizer [for example, Oligo 1000M DNA Synthesizer (Beckman) or 394 DNA/RNA Synthesizer (Applied Biosystems)].

Those skilled in the art may prepare a polynucleotide encoding a polypeptide having an activity similar to a naturally-occurring activity inhibiting glucose uptake into an adipocyte by an insulin stimulation, by performing modifications, such as substitution, deletion, and/or addition, in a part of a naturally-occurring base sequence. A polynucleotide encoding the variation functionally equivalent or homologous polypeptide having an inhibitory activity the same as that of a naturally-occurring polypeptide may be prepared by, for example, an introduction of deletion by a restriction enzyme and/or DNA exonuclease, an introduction of variations by site-specific mutagenesis [Nucleic Acid Res. 10, 6487 (1982)], a direct introduction of a synthetic mutant DNA [Maniatis, T. et al. (1989) “Molecular Cloning—A Laboratory Manual 2^(nd) Edt.” Cold Spring Harbor Laboratory, NY], or the like.

Determination of the DNA sequences obtained by the above-mentioned methods can be carried out by, for example, a Maxam-Gilbert chemical modification method (Maxam, A. M. and Gilbert, W., “Methods in Enzymology”, 65, 499-559, 1980) or a dideoxynucleotide chain termination method (Messing, J. and Vieira, J., Gene, 19, 269-276, 1982).

An isolated polynucleotide of the present invention or polynucleotide for a screening tool is re-integrated into an appropriate vector DNA and a host cell (including a eucaryotic host cell and a procaryotic host cell) may be transformed by the resulting expression vector. Further, it is possible to express the polynucleotide in a desired host cell, by introducing an appropriate promoter and a sequence related to the gene expression into the vector.

In the eucaryotic host cells, for example, cells of vertebrates, insects, and yeast are included. As the vertebral cell, there may be mentioned, for example, a simian COS cell (Gluzman, Y., Cell, 23, 175-182, 1981), a dihydrofolate reductase defective strain of a Chinese hamster ovary cell (CHO) (Urlaub, G. and Chasin, L. A., Proc. Natl. Acad. Sci. USA, 77, 4216-4220, 1980), a human fetal kidney derived HEK293 cell, or a 293-EBNA cell (Invitrogen) obtained by introducing an EBNA-1 gene of Epstein Barr Virus into HEK293 cell.

As an expression vector for a vertebral cell, a vector containing a promoter positioned upstream of the polynucleotide to be expressed, an RNA splicing site, a polyadenylation site, a transcription termination sequence, and the like may be generally used. The vector may further contain a replication origin, if necessary. As the expression vector, there may be mentioned, for example, pSV2dhfr containing an SV40 early promoter (Subramani, S. et al., Mol. Cell. Biol., 1, 854-864, 1981), pEF-BOS containing a human elongation factor promoter (Mizushima, S. and Nagata, S., Nucleic Acids Res., 18,5322, 1990), or pCEP4 containing a cytomegalovirus promoter (Invitrogen).

When the COS cell is used as the host cell, a vector which has an SV40 replication origin, can perform an autonomous replication in the COS cell, and has a transcription promoter, a transcription termination signal, and an RNA splicing site, may be used as the expression vector. As the vector, there may be mentioned, for example, pME18S (Maruyama, K. and Takebe, Y., Med. Immunol., 20, 27-32, 1990), pEF-BOS (Mizushima, S. and Nagata, S., Nucleic Acids Res., 18, 5322, 1990), or pCDM8 (Seed, B., Nature, 329, 840-842, 1987).

The expression vector may be incorporated into COS cells by, for example, a method using a commercially available transfection reagent (for example, FuGENE™6 Transfection Reagent; Roche Diagnostics).

When the CHO cell is used as the host cell, a transformant capable of stably producing the polypeptide of the present invention or the polynucleotide for a screening tool can be obtained by carrying out a co-transfection of an expression vector comprising the polynucleotide of the present invention or the polynucleotide for a screening tool, together with a vector capable of expressing a neo gene which functions as a G418 resistance marker, such as pRSVneo (Sambrook, J. et al., “Molecular Cloning-A Laboratory Manual”, Cold Spring Harbor Laboratory, NY, 1989) or pSV2-neo (Southern, P. J. and Berg, P., J. Mol. Appl. Genet., 1, 327-341,1982), and selecting a G418 resistant colony.

When the 293-EBNA cell is used as the host cell, for example, pCEP4 (Invitrogen) containing a replication origin of Epstein Barr Virus and capable of performing an autonomous replication in the 293-EBNA cell may be used as the expression vector.

The transformant may be cultured in accordance with the conventional method, and the polypeptide of the present invention or the polynucleotide for a screening tool is transmembranously produced. As a medium to be used in the culturing, a medium commonly used in a desired host cell may be appropriately selected. In the case of the COS cell, for example, a medium such as an RPMI-1640 medium or a Dulbecco's modified Eagle's minimum essential medium (DMEM) may be used, by supplementing it with a serum component such as fetal bovine serum (FBS) if necessary. In the case of the 293-EBNA cell, a medium such as a Dulbecco's modified Eagle's minimum essential medium (DMEM) with a serum component such as fetal bovine serum (FBS) and G418 may be used.

The polypeptide of the present invention or the polynucleotide for a screening tool produced by culturing the transformants of the present invention may be separated and purified therefrom by various known separation techniques making use of the physical properties, chemical properties and the like of the polypeptide. More particularly, the above polypeptide may be purified by treating the cells or cell membrane fraction containing the polypeptide with a commonly used treatment, for example, a treatment with a protein precipitant, ultrafiltration, various liquid chromatography techniques such as molecular sieve chromatography (gel filtration), adsorption chromatography, ion exchange chromatography, affinity chromatography, or high performance liquid chromatography (HPLC), or dialysis, or a combination thereof.

When the polypeptide of the present invention or the polynucleotide for a screening tool is expressed as a fusion protein with a marker sequence in frame, identification of the expression of the polypeptide, purification thereof, or the like may be easily carried out. As the marker sequence, there may be mentioned, for example, a FLAG epitope, a hexa-histidine tag, a hemagglutinin tag, or a myc epitope. Further, by inserting a specific amino acid sequence recognized by a protease such as enterokinase, factor Xa, or thrombin between the marker sequence and the polypeptide, the marker sequence may be removed by the protease.

4. Method for Producing the Promoter and the Cell Expressing the Promoter of the Present Invention

The promoter of the present invention may be prepared by the following methods, as well as by the method described in Example 11.

(1) Preparation Using the PCR Method

As described in Example 11, PCR is carried out using primers and human genomic DNA to prepare a DNA comprising the base sequence consisting of the 34th to 2014th bases in the base sequence of SEQ ID NO: 20. Generally, allele variations are well-known. When DNAs are prepared by the above method, a polynucleotide exhibiting the promoter activity of the polypeptide for a screening tool of the present invention and comprising a base sequence in which one or more bases are substituted, deleted, and/or inserted at any position in the base sequence consisting of the 34th to 2014th bases in the base sequence of SEQ ID NO: 20, may be sometimes obtained. Such a polynucleotide is also included in the promoter of the present invention as described above.

(2) Preparation Using DNA Synthesis

The polynucleotide may be prepared by chemically synthesizing and binding DNA fragments which are divided from the base sequence consisting of the 34th to 2014th bases in the base sequence of SEQ ID NO: 20 and the chain complementary thereto. The DNA fragments can be synthesized by a DNA synthesizer.

It may be confirmed whether or not the obtained polynucleotide exhibits the promoter activity of the polypeptide for a screening tool of the present invention (or the polypeptide of the present invention) by, for example, the method described in Example 12.

Those skilled in the art may prepare a polynucleotide having a promoter activity similar to that of a naturally-occurring promoter, by performing modifications, such as substitution, deletion, and/or addition, in a part of the base sequence of a naturally-occurring promoter sequence. A polynucleotide having a base sequence in which one or more bases are substituted, deleted, and/or added in a naturally-occurring base sequence and having a promoter activity similar to that of a naturally-occurring promoter, is included in the promoter of the present invention as described above. The base modifications may be carried out by, for example, an introduction of deletion by a restriction enzyme and/or DNA exonuclease, an introduction of variations by site-specific mutagenesis, a modification of a promoter sequence by the PCR method using mutant primers, a direct introduction of a synthetic mutant DNA, or the like.

The cell expressing the promoter of the present invention may be prepared by incorporating the promoter of the present invention into a host cell appropriately selected in accordance with the object. It is preferable to prepare the cell by incorporating the promoter of the present invention into a vector appropriately selected in accordance with the object. For example, when a system for analyzing the inhibition of a promoter activity is constructed, it is preferable to prepare the cell by incorporating the promoter of the present invention into a vector having a reporter gene such as luciferase, as described in Examples 11 and 12. For example, when a system for screening a substance capable of controlling the activity of the promoter of the present-invention, preferably a cell derived from a mammal such as human, mouse, rat, or the like, more preferably a cell derived from a human, may be used.

5. Analysis Method and Screening Method of the Present Invention

(1) Method Using the Polypeptide for a Screening Tool or the Cell for a Screening Tool

An analysis whether or not a substance to be tested inhibits the activity of the polypeptide for a screening tool and a screening of an inhibitor therefor may be carried out, by utilizing the activity of inhibiting glucose uptake into an adipocyte by an insulin stimulation. The inhibitor for the polypeptide is useful as an active ingredient of an agent for treating or preventing diabetes (preferably type II diabetes, particularly insulin resistance), and thus it is possible to screen a therapeutic agent for diabetes (preferably type II diabetes, particularly insulin resistance).

The method of the present invention for analyzing whether or not a substance to be tested is an inhibitor of the polypeptide for a screening tool comprises the steps of:

-   bringing a cell expressing the polypeptide for a screening tool into     contact with the substance to be tested, and -   analyzing an amount of glucose uptake by an insulin stimulation. The     method for screening an inhibitor of the polypeptide for a screening     tool or a therapeutic agent for diabetes comprises the steps of: -   analyzing a substance to be tested by the above method, and     selecting an inhibitor.

More particularly, for example, adipocytes, or cells (such as 3T3-L1 cells) obtained by-differentiating cells other than the adipocyte into adipocytes may be used as the cells expressing the polypeptide for a screening tool. It is preferable to use the cells which are differentiated from the 3T3-L1 cells into adipocytes and express the polypeptide of SEQ ID NO: 2 or SEQ ID NO: 14, used in Example 7 (Ezaki et al., “IGAKU NO AYUMI (Journal of Clinical and Experimental Medicine”, 503-506, 1998).

An amount of glucose uptake can be analyzed (detected or measured) in accordance with a conventional method. The method described in Example 7 is preferable as the analysis method. More particularly, an amount of glucose uptake when bringing the test substance into contact with the cells expressing the polypeptide, and an amount of glucose uptake without the contact are measured, respectively. It can be judged that a test substance in which the amount of glucose uptake when the test substance is brought into contact with the cells is increased in comparison with that without the contact is the inhibitor of the polypeptide, and thus is useful as an active ingredient of an agent for treating or preventing diabetes (preferably type II diabetes, particularly insulin resistance).

When an inhibitor of the polypeptide for a screening tool is selected by the screening method of the present invention, a degree of increase in the amount of glucose uptake is preferably 20% or more, more preferably 50% or more, most preferably 80% or more.

(2) Method Using the Promoter-type Screening Tool of the Present Invention

The analysis method of the present invention includes the method for analyzing whether or not a substance to be tested-inhibits an activity of the promoter of the present invention, comprising the steps of:

-   bringing the cell expressing the promoter of the present invention     (preferably the cell transformed with the expression vector     containing the promoter of the present invention) into contact with     the substance to be tested, and analyzing (detecting or measuring)     the promoter activity.

As the method for analyzing the promote activity, a method using a reporter gene plasmid comprising the base sequence consisting the 34th to 2014th bases in the base sequence of SEQ ID NO: 20 described in Example 12 is convenient. The reporter gene is a gene encoding a protein which can be quantified by a conventional method (known quantifying methods such as measurement of an enzyme activity or the like). As the reporter gene, for example, each gene of chloramphenicol acetyl transferase, luciferase, β-galactosidase, or alkaline phosphatase is often used, but is not limited. The original vector for constructing the reporter gene plasmid is not limited, but commercially available plasmid vectors, such as pGV-B2 (Toyo Ink MFG) or pSEAP2-Basic (Clontech), may be used. The existence and/or strength of the promoter activity of the sequence can be determined by constructing the reporter gene plasmid in which the sequence is incorporated in the forward direction upstream of the reporter gene in the vector, and then measuring an amount of the reporter protein expressed in the cells transformed with the plasmid in accordance with an appropriate method. Further, an action of a test substance with respect to the promoter activity can be analyzed by adding the test substance to culture medium of the transformant.

The present invention includes a method for screening a substance which inhibits an expression of the polypeptide for a screening tool of the present invention (preferably the polypeptide of the present invention), or a method for screening a therapeutic agent for diabetes (particularly an agent for alleviating insulin resistance), comprising the steps of:

-   analyzing a substance to be tested described above, and selecting a     substance which inhibits the promoter activity.

As the substance which inhibits the promoter activity selected by the screening method, a substance which inhibits it by 20% or more in accordance with the method described in Example 12 is preferable, a substance which inhibits it by 50% or more is more preferable, and a substance which inhibits it by 80% or more is most preferable;

Compounds to be tested which may be applied to the screening method of the present invention are not particularly limited, but there may be mentioned, for example, various known compounds (including peptides, or antibodies or fragments thereof) registered in chemical files, commercially available compounds, compounds obtained by combinatorial chemistry techniques (Terrett, N. K. et al., Tetrahedron, 51, 8135-8137, 1995) or conventional synthesis techniques, random peptides prepared by employing a phage display method (Felici, F. et al., J. Mol. Biol., 222, 301-310, 1991), culture supernatants of microorganisms, natural components derived from plants or marine organisms, animal tissue extracts, or the like. Further, compounds (including peptides, or antibodies or fragments thereof) obtained by chemically or biologically modifying compounds (including peptides) selected by the screening method of the present invention may be used.

6. Process for Manufacturing the Pharmaceutical Composition for Treating Diabetes of the Present Invention

The process for manufacturing the pharmaceutical composition for treating diabetes (including pharmaceutical composition for treating and preventing diabetes) of the present invention comprises the steps of:

-   (i) (a) analyzing an inhibitor using the cell for a screening tool     of the present invention or (b) analyzing a promoter activity using     the promoter-type screening tool of the present invention, as     described above, and -   (II) preparing a medicament containing the substance.

The process for manufacturing a pharmaceutical composition for treating diabetes of the present invention includes a process for manufacturing a pharmaceutical composition for treating diabetes comprising the steps of:

-   analyzing, in a quality control test of a pharmaceutical composition     for treating diabetes, whether or not the pharmaceutical composition     inhibits the activity of inhibiting glucose uptake by an insulin     stimulation or the promoter activity, by the analysis method of the     present invention, and preparing a medicament.

The present invention includes a pharmaceutical composition for treating diabetes comprising as an active ingredient a substance which inhibits the activity of inhibiting glucose uptake by an insulin stimulation or the promoter activity, selected by the screening method of the present invention. The process of the present invention for manufacturing a pharmaceutical composition for treating diabetes includes a process for manufacturing a pharmaceutical composition for treating diabetes comprising the step of preparing a medicament containing the substance selected by the screening method of the present invention comprising the above-described analysis step of the present invention.

A DNA comprising at least a part of the base sequence of SEQ ID NO: 20 can competitively inhibit the binding between the promoter of the present invention and a protein (for example, a transcription factor) capable of binding thereto, independently of having the promoter activity. Therefore, when the above DNA corresponds to the binding site of a protein capable of promoting the activity of the promoter of the present invention, the promoter activity can be inhibited by administering the DNA. The DNA used for the competitive inhibition has generally a length of at least of 6 bases or more, preferably 10 bases or more.

The pharmaceutical composition of the present invention may be prepared using carriers, fillers, and/or other additives generally used in the preparation of medicaments, in accordance with the active ingredient.

Examples of administration include oral administration by tablets, pills, capsules, granules, fine granules, powders, oral solutions and the like, and parenteral administration by injections (e.g., intravenous, intramuscular, or the like), suppositories, transdermal preparations, transmucosal absorption preparations and the like. Particularly, in the case of peptides which are digested in the stomach, a parenteral administration such as an intravenous injection or the like, or preparation techniques in which the polypeptide is not digested, such as a preparation technique disclosed in the WO95/28963 pamphlet, is preferable.

In the solid composition for use in the oral administration, one or more active substances may be mixed with at least one inert diluent such as lactose, mannitol, glucose, microcrystalline cellulose, hydroxypropylcellulose, starch, polyvinyl pyrrolidone, or aluminum magnesium silicate. In the usual way, the composition may contain additives other than the inert diluent, such as a lubricant, a disintegrating agent, a stabilizing agent, or a solubilizing or solubilization assisting agent. If necessary, tablets or pills may be coated with a sugar coating or a film of a gastric or enteric substance.

The liquid composition for oral administration may include, for example, emulsions, solutions, suspensions, syrups, and elixirs, and may contain a generally used inert diluent such as purified water or ethyl alcohol. The composition may contain additives other than the inert diluent, such as moistening agents, suspending agents, sweeteners, flavors, or antiseptics.

The injections for parenteral administration may include aseptic aqueous or non-aqueous solutions, suspensions, and emulsions. Examples of the diluent for use in the aqueous solutions and suspensions include distilled water for injection use and physiological saline. Examples of the diluent for use in the non-aqueous solutions and suspensions include propylene glycol, polyethylene glycol, plant oil (e.g., olive oil), alcohols (e.g., ethanol), polysorbate 80 and the like. Such a composition may further contain a moistening agent, an emulsifying agent, a dispersing agent, a stabilizing agent, a solubilizing or solubilization assisting agent, an antiseptic or the like. These compositions may be sterilized, for example, by filtration through a bacteria retaining filter, blending of a germicide, or irradiation. Alternatively, they may be used by first making them into sterile solid compositions and dissolving them in sterile water or other sterile solvent for injection use prior to their use.

The dose is optionally decided by taking into consideration the strength of each active ingredient selected by the aforementioned screening method, or symptoms, age, sex, or the like of each patient to be administered.

For example, in the case of oral administration, the usual dosage for an adult (60 kg in weight) is about 0.01 to 1000 mg, preferably 0.01 to 100 mg per day. In the case of parenteral administration, the usual dosage is about 0.01 to 1000 mg, preferably 0.01 to 100 mg per day in the form of an injection.

7. Probe of the Present Invention

The present invention includes a probe which hybridizes to the polynucleotide of the present invention under stringent conditions.

The term “stringent conditions” as used herein means the conditions as described above.

The probe of the present invention may be used for examining an amount of expression of the polynucleotide encoding the polypeptide of the present invention (particularly the polypeptide consisting of the amino acid sequence of SEQ ID NO: 2). Diabetes can be diagnosed by the increased amount of the expression (preferably expression in adipocytes) as an indicator.

As described above, the present invention includes a method for detecting diabetes using the probe of the present invention. According to the detection method of the present invention, diabetes can be detected by bringing the probe of the present invention into contact with a sample to be tested, and then analyzing a complex of the polynucleotide (such as mRNA, or cDNA derived therefrom) encoding the polypeptide (particularly the polypeptide consisting of the amino acid sequence of SEQ ID NO: 2) of the present invention and the probe by a known analysis method (such as northern blotting). Further, the probe of the present invention can be applied to a gene chip to analyze an amount of expression. When the amount of the complex, i.e, the amount of the polynucleotide encoding the polypeptide of the present invention, is increased in comparison with that of a healthy person, it can be judged that the patient suffers from diabetes.

EXAMPLES

The present invention now will be further illustrated by, but is by no means limited to, the following Examples. The procedures were performed in accordance with known methods described in laboratory manuals for genetic engineering (for example, Sambrook, J. et al., “Molecular Cloning-A Laboratory Manual”, Cold Spring Harbor Laboratory, NY, 1989), unless otherwise specified.

Example 1 Cloning of Human MD8 Gene and Construction of Expression Vectors

(1) Cloning of Human MD8 cDNA

A polymerase chain reaction (PCR) was performed to obtain a human ortholog gene corresponding to the gene of GenBank Accession No. X13335. In the PCR, human placenta cDNA (Marathon-Ready™ cDNA; Clontech) was used as a template, oligo DNA consisting of the base sequence of SEQ ID NO: 6 and oligo DNA consisting of the base sequence of SEQ ID NO: 7 were used as primers, and LAtaqDNA polymerase (Takara Shuzo) was used. The PCR was carried out by performing a reaction at 94° C. for 2 minutes and then repeating a cycle consisting of reactions at 98° C. for 20 seconds and at 68° C. for 2 minutes and 30 seconds 40 times. A DNA fragment of approximately 2.5 kbp was separated and extracted as a template solution A by an agarose electrophoresis.

PCR was performed by using the resulting template solution A as a template to obtain a DNA fragment A of approximately 2.0 kbp. In the PCR, oligo DNA consisting of the base sequence of SEQ ID NO: 8 (having the restriction enzyme XbaI recognition sequence added to the base sequence consisting of the 1st to 18th bases in the base sequence of SEQ ID NO: 1) and oligo DNA consisting of the base sequence of SEQ ID NO: 9 (having the restriction enzyme BamHI recognition sequence added to the base sequence complementary to that consisting of the 1918th to 1938th bases in the base sequence of SEQ ID NO: 1) were used as primers, and DNA polymerase (Pyrobest DNA polymerase; Takara Shuzo) was used. The PCR was carried out by performing a reaction at 94° C. for 2 minutes, repeating a cycle consisting of reactions at 98° C. for 20 seconds, at 60° C. for 30 seconds, and at 72° C. for 2 minutes and 30 seconds 15 times, and performing a reaction at 72° C. for 7 minutes.

Similarly, PCR was performed by using the template solution A as a template to obtain a DNA fragment B of approximately 0.7 kbp. In the PCR, oligo DNA consisting of the base sequence of SEQ ID NO: 10 (base sequence consisting of the 1795th to 1824th bases in the base sequence of SEQ ID NO: 1) and oligo DNA consisting of the base sequence of SEQ ID NO: 11 (having the restriction enzyme BamHI recognition sequence added to the base sequence complementary to that consisting of the 2443rd to 2472nd bases-in the base sequence of SEQ ID NO: 1) were used as primers, and DNA polymerase (Pyrobest DNA polymerase; Takara Shuzo) was used. The PCR was carried out by performing a reaction at 94° C. for 2 minutes, repeating a cycle consisting of reactions at 98° C. for 20 seconds, at 60° C. for 30 seconds, and at 72° C. for 1 minute 15 times, and performing a reaction at 72° C. for 7 minutes.

The resulting DNA fragments A and B were independently subcloned at the EcoRV site of plasmid pZErO2.1 (Invitrogen). The base sequences of the resulting plasmids (designated pzErO-MD8A and pZErO-MD8B, respectively) was analyzed using a DNA sequencer (ABI3700 DNA Sequencer; Applied Biosystems) by a dideoxy terminator method to obtain an ORF consisting of the base sequence of SEQ ID NO: 1. As a result, neither the base sequence of SEQ ID NO: 1 nor the amino acid sequence of SEQ ID NO: 2 deduced from the base sequence was found in the registered sequences of GenBank and SwissProt, and it was found that those of SEQ ID NOS: 1 and 2 are novel. In this connection, as a known base sequence in which a base is different from that of SEQ ID NO: 1 and a known amino acid sequence in which an amino acid is different from that of SEQ ID NO: 2, the base sequence of GenBank Accession No. D26579 and the amino acid sequence of SwissProt Accession No. BAA05626 exist, respectively. The known sequence is designated as “ADAM8”, but the relationship between ADAM8 and diabetes is not known.

Hereinafter, the protein encoded by the ORF (i.e., polypeptide consisting of the amino acid sequence consisting of the 1st to 824th amino acids in the amino acid sequence of SEQ ID NO: 2) is referred to as “human MD8”.

(2) Construction of Vector for Expressing Human MD8 Full-length Protein (MD8)

A DNA fragment of approximately 1.8 kbp generated by digesting the plasmid pZErO-MD8A obtained in Example 1(1) with restriction enzymes XbaI and BstYI, and a DNA fragment of approximately 0.6 kbp generated by digesting the plasmid pZErO-MD8A obtained in Example 1(1) with restriction enzymes BstYI and BamHI were inserted between the XbaI site and BamHI site of plasmid pCEPdE2-FLAG (Example 7-1 in WO01/34785) to construct a plasmid pCEPdE2-MD8-FLAG for expressing a protein MD8-FLAG in which a FLAG tag of SEQ ID NO: 12 was added to the C-terminus of the MD8 protein.

(3) Construction of Vector for Expressing MD8 Extracellular Protein (MD8s)

A DNA fragment of approximately 2.0 kbp generated by digesting the plasmid pZErO-MD8A obtained in Example 1(1) with restriction enzymes XbaI and BamHI was inserted between the XbaI site and BamHI site of plasmid pCEPdE2-FLAG to construct a plasmid pCEPdE2-MD8S-FLAG for expressing a protein MD8S-FLAG in which a FLAG tag of SEQ ID NO: 12 was added to the C-terminus of the amino acid sequence consisting of the 1st to 646th amino acids, corresponding to an extracellular region of the MD8 protein (hereinafter referred to as MD8S), in the amino acid sequence of SEQ ID NO: 2.

Example 2 Expression of MD8S Protein and MD8 Protein in Animal Cell Strain

The expression plasmid pCEPdE2-MD8S-FLAG prepared in Example 1(3) was introduced into HEK293-EBNA cells (Invitrogen) with a transfection reagent (FuGENE™6 Transfection Reagent; Boeringer Mannheim) in accordance with a manual attached to the reagent to express the MD8S protein. After the introduction of the plasmid, it was confirmed by western blotting using an antibody-against the FLAG tag added to the C-terminus (mouse anti-FLAG monoclonal antibody M2; Sigma) that the protein of interest (i.e., MD8S-FLAG protein) was contained in a culture supernatant obtained by culturing for 2 days.

More particularly, the culture supernatant was electrophoresed using an SDS/4%-20% acrylamide gel (Daiichi Pure Chemicals) and transferred onto a polyvinylidene difluoride (PVDF) membrane using a blotting apparatus. After the transfer, the PVDF membrane was blocked by adding a blocking reagent (Block Ace; Dainippon pharmaceutical), and reacted with the mouse anti-FLAG monoclonal antibody M2, followed by a horseradish peroxidase-labeled rabbit anti-mouse IgG polyclonal antibody (Zymed or TAGO). Alternatively, after blocking, the membrane was reacted with a biotinylated M2 antibody (Sigma), followed by a horseradish peroxidase-labeled streptavidin (Amersham). After the reaction, the expression of the protein of interest was confirmed using an ECL western blotting detection system (Amersham Pharmacia). The expressed proteins were detected as two bands. One molecular weight was approximately 90 kDa, which was identical to the value calculated from the amino acid sequence thereof, and the other was approximately 67 kDa, which was approximately 23 kDa smaller.

Similarly, the MD8 protein was expressed by using the expression plasmid pCEPdE2-MD8-FLAG prepared in Example 1(2). In this connection, since the MD8 protein contains a transmembrane region, the expression was confirmed by western blotting a cell fraction after 2 days from the plasmid introduction and detecting a 100 kDa band.

Example 3 Cloning of Mouse MD8 Gene

PCR was performed to obtain a gene of which the expression was increased in a diabetes model as shown in Referential Example described below, by using mouse 11-day embryo cDNA and mouse 17-day embryo cDNA (Marathon-Ready cDNA; Clontech) as a template, DNA consisting of the base sequence of SEQ ID NO: 16 as a 5′ primer, DNA consisting of the base sequence of SEQ ID NO: 17 as a 3′ primer, and LAtaqDNA polymerase (Takara Shuzo). The PCR was carried out by performing a reaction at 94° C. for 2 minutes and then repeating a cycle consisting of reactions at 98° C. for 10 seconds, at 60° C. for 30 seconds, and at 68° C. for 2 minutes and 30 seconds 40 times. The resulting DNA fragments of approximately 3.6 kbp and approximately 2.5 kbp were separated and extracted by an agarose electrophoresis. The base sequences of the fragments were analyzed using a DNA sequencer (ABI3700 DNA Sequencer; Applied Biosystems) by a dideoxy terminator method to determine an ORF consisting of the base sequence of SEQ ID NO: 13.

As a result, the base sequence of the DNA fragment (approximately 3.6 kbp) generated from the 11-day embryo accorded with that of the DNA fragment (approximately 2.5 kbp) generated from the 17-day embryo, except that the approximately 3.6 kbp fragment from the 11-day embryo contained an insertion of approximately 1.0 kbp which did not exist in the approximately 2.5 kbp fragment from the 17-day embryo and the X13335 gene. Further, it was found that the base sequence of the approximately 2.5 kbp fragment was different at three positions (two positions with respect to the deduced amino acid sequence) from that of X13335. The approximately 2.5 kbp DNA fragment generated from the 17-day embryo was subcloned into pCR2.1 (Invitrogen) to obtain pCR-mMD8L.

Example 4 Construction of Adenovirus Vector for Expressing MD8 and Preparation of Adenovirus Solution

(1) Construction of Adenovirus Vector for Expressing Mouse MD8 and Preparation of Adenovirus Solution

PCR was performed by using pCR-mMD8L as a template, DNA consisting of the base sequence of SEQ ID NO: 18 as a 5′ primer, DNA consisting of the base sequence of SEQ ID NO: 19 as a 3′ primer, and DNA polymerase (Pyrobest DNA polymerase; Takara Shuzo). The PCR was carried out by performing a reaction at 94° C. for 2 minutes, repeating a cycle consisting of reactions at 98° C. for 20 seconds, at 55° C. for 30 seconds, and at 72° C. for 3 minutes 15 times, and performing a reaction at 72° C. for 7 minutes. The resulting DNA fragment of approximately 2.5 kbp was inserted at the EcoRV site of plasmid pZErO2.1 (Invitrogen) to construct pZErO-mMD8L. The plasmid was digested with a restriction enzyme XbaI, and then the resulting DNA fragment of approximately 2.5 kbp was inserted into and ligated with a pAdTrack-CMV vector (He T. C. et al., Proc. Natl. Acad. Sci. USA., 95, 2509-2514, 1998), which had been previously digested with a restriction enzyme XbaI and dephosphorylated with alkaline phosphatase (BAPC75; Takara Shuzo). Among the clones, a clone in which the ORF of mMD8 was located in the direction similar to the CMV promoter was selected to designated pAdTrack-CMV-mMD8. Thereafter, an adenovirus solution having a high titer and expressing mMD8 (hereinafter referred to as an mMD8 virus) was prepared in accordance with a known protocol [“A Practical Guide for using the AdEasy System” (available on the internet at “coloncancer.org/adeasy.htm” coloncancer.org/adeasy/protocol2.htm)]. A control adenovirus solution (hereinafter referred to as a control virus) was prepared using pAdTrack-CMV instead of pAdTrack-CMV-mMD8.

(2) Construction of Adenovirus Vector for Expressing Human MD8 and Preparation of Adenovirus Solution

PCR was performed by using pCEPdE2-MD8-FLAG prepared in Example 1(2) as a template, DNA consisting of the base sequence of SEQ ID NO: 23 as a 5′ primer, DNA consisting of the base sequence of SEQ ID NO: 24 as a 3′ primer, and DNA polymerase (Pyrobest DNA polymerase; Takara Shuzo). The PCR was carried out by performing a reaction at 95° C. for 2 minutes, repeating a cycle consisting of reactions at 98° C. for 20 seconds, at 55° C. for 30 seconds, and at 72° C. for 3 minutes 15 times, and performing a reaction at 72° C. for 7 minutes. The resulting DNA fragment of approximately 2.5 kbp was inserted at the EcoRV site of plasmid pZErO2.1 (Invitrogen) to construct pZErO-MD8-FLAG. The plasmid was digested with a restriction enzyme Bg1II, and then the resulting DNA fragment of approximately 2.5 kbp was inserted into and ligated with a pAdTrack-CMV vector (He T. C. et al., Proc. Natl. Acad. Sci. USA., 95, 2509-2514, 1998), which had been previously digested with a restriction enzyme Bg1II and dephosphorylated with alkaline phosphatase (BAPC75; Takara Shuzo). Among the clones, a clone in which the MD8-FLAG gene was located in the direction similar to the CMV promoter was selected to designated pAdTrack-CMV-MD8-FLAG. Hereinafter, an adenovirus solution having a high titer and expressing human MD8 (hereinafter referred to as an MD8 virus) was prepared in a manner similar to that in Example 4(1).

Example 5 Differentiation of 3T3-L1 to Adipocyte

A method for differentiation of a mouse 3T3-L1 cell (ATCC No.: CL-173) to an adipocyte was basically carried out in accordance with a known method (Ezaki et al., “IGAKU NO AYUMI (Journal of Clinical and Experimental Medicine”, 503-506, 1998). The 3T3-L1 cell is a mouse-derived cultured cell strain which is widely used as a model cell of a white adipocyte.

The 3T3-L1 cells were plated on a 24-well collagen-coated plate (ASAHI TECHNO GLASS) to become 50000 cells per well. When the cells were confluent, the medium was changed to a Dulbecco's modified Eagle's medium (DMEM) supplemented with 0.5 mmol/L 3-isobutyl-l-methylxanthine, 0.25 μmol/L dexamethasone, and 10 μg/mL insulin and containing 10% fetal bovine serum to start the differentiation to adipocytes. After 2 days, the medium was changed to DMEM supplemented with only 1 μg/mL insulin and containing 10% fetal bovine serum, and then the medium change was repeated every three days to start an induction of differentiation.

Example 6 Infection of Adenovirus Vector

(1) Preparation of Cells Infected with mMD8 Virus

The mMD8 virus solution prepared in Example 4(1) was diluted with the medium to 100 μL (2.2×10⁹ viruses per well of a 24-well plate). The dilution was added to 3T3-L1 cells after 4 days from the induction of differentiation, without the cultured medium, to start infection. The plate was shaken every 20 minutes, and after shaking at 60 minutes, 400 μL of the medium was added and the culture was continued. A multiplicity of infection was calculated by visually observing fluorescence generated from green fluorescent protein (GFP) integrated into the prepared adenovirus by a fluorescent microscope, as a percentage of cells with fluorescence to all cells. To perform an experiment in glucose uptake shown in the following Examples, the 3T3-L1 cells cultured on the 24-well plate were divided into two groups, and infected with the mMD8 virus or control virus prepared in Example 4(1).

(2) Preparation of Cells Infected with MD8 Virus

The MD8 virus solution prepared in Example 4(2) was treated in a manner similar to that in Example 6(1), except for diluting the solution to 2.9×10⁹ viruses per well of a 24-well plate, to prepare groups of 3T3-L1 cells infected with the MD8 virus or control virus prepared in Example 4(2).

Example 7 Measurement of Amount of Glucose Uptake into Adipocyte

The 3T3-L1 cells infected with adenovirus in Example 6 were cultured for 2 days, to progress infection and differentiation to adipocytes simultaneously. At the night after 7 days from the induction of differentiation, each well was washed twice with DMEM without serum, 500 μL of DMEM without serum was added to each well, and the plate was allowed to stand for a day. At the experimental day, each well was washed twice with a KRP buffer (136 mmol/L NaCl, 4.7 mmol/L KCl, 1.25 mmol/L CaCl₂, 1.25 mmol/L MgSO₄, and 5 mmol/L Na₂HPO₄), and the KRP buffer containing 1 μmol/L of insulin was added and incubated for 20 minutes. The similar procedure was performed except for using the KRP buffer without insulin, as a control.

To each well, 0.2 mmol/L 2-deoxyglucose (Wako Pure Chemical Industries) and 5.55 kBq 2-deoxy-D-(U-¹⁴C) glucose (Amersham) was added and incubated for 10 minutes to chase glucose uptake. After washing three times with the ice-cold KRP buffer, cells were lysed with 150 μL of a 0.2% SDS solution and mixed well with aquasol-2 (Packard) to measure radioactivity incorporated into cells by a liquid scintillation counter (Packard).

The results when using the cells prepared in Example 6(1) are shown in FIG. 1. An amount of glucose uptake by an insulin stimulation was increased by approximately 3.4-fold in the adipocyte infected with the control virus, whereas the amount was increased by only approximately 2.4-fold in the adipocyte infected with the mMD8 virus. It is considered from the results that mMD8 inhibits glucose uptake. In this connection, the multiplicity of infection in this experiment was approximately 50%.

The results when using the cells prepared in Example 6(2) are shown in FIG. 2. An amount of glucose uptake by an insulin stimulation was increased by approximately 4.0-fold, in comparison to nonstimulation, in the adipocyte infected with the control virus, whereas the amount was increased by only approximately 2.0-fold, in comparison to nonstimulation, in the adipocyte infected with the MD8 virus. Similarly to mMD8, it is considered from the results that MD8 inhibits glucose uptake. In this connection, the multiplicity of infection in this experiment was approximately 70%.

Example 8 Confirmation of Activity of Digesting IGFBP by MD8S Protein

(1) Preparation of Purified MD8S Enzyme Solution

The expression plasmid pCEPdE2-MD8S-FLAG prepared in Example 1(3) was introduced into HEK293-EBNA cells (Invitrogen) with a transfection reagent (FuGENE™6 Transfection Reagent; Boeringer Mannheim) in accordance with a manual attached to the reagent. After 16 hours from the introduction of the expression plasmid, the medium was changed to a serum-free medium. The culture was continued for 2 days to collect the culture supernatant.

The MD8S protein from the culture supernatant was purified by affinity utilizing the FLAG tag added to the C-terminus. More particularly, the culture supernatant was applied to an M2-agarose (Sigma) column, the column was washed with 20 mmol/L tris-HCl(pH7.4)/150 mmol/L NaCl (hereinafter referred to as TBS), and elution and fractionation were performed with 100 μg/mL FLAG peptide (Sigma) in TBS to obtain an MD8S enzyme solution.

(2) Confirmation of Activity of Digesting IGFBP by MD8S Protein

The MD8S enzyme solution obtained in Example 8(1) was reacted with commercially available IGFBP-3 or IGFBP-5 (upstate biotechnology) in a 50 mmol/L tris-HCl(pH7.4) buffer containing 50 mmol/L NaCl, 2 mmol/L CaCl₂, 20 μg/mL bovine serum albumin (BSA), and 0.1% CHAPS at 37° C. overnight. In this connection, concentrations of the MD8S protein and IGFBP-3 (or IGFBP-5) in the reaction solution were 1.5 μg/mL and 10 μg/mL, respectively.

Using an aliquot of the reaction solution, sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) was carried out, and then a transfer to a PVDF membrane and blocking was carried out. IGFBP-3 was detected using an anti-IGFBP-3 polyclonal antibody (R&D System) as the first antibody and a peroxidase-labeled rabbit anti-goat IgG polyclonal antibody (ZYMED) as the second antibody. IGFBP-5 was detected using an anti-IGFBP-5 polyclonal antibody (upstate biotechnology) as the first antibody and a peroxidase-labeled goat anti-rabbit IgG polyclonal antibody (MBL) as the second antibody.

IGFBP-3 and IGFBP-5 were detected at approximately 45 kDa and 30 kDa, respectively. When the MD8S enzyme solution was added to each, a new band of 25 kDa was detected in the case of IGFBP-3, and new plural bands within the range of 12 to 25 kDa were detected in the case of IGFBP-5. It was found from the results that the MD8S protein exhibits an activity of digesting IGFBP-3 and IGFBP-5.

Example 9 Confirmation of Activity of Digesting Recombinant IGFBP-5 by MD8S

(1) Preparation of Recombinant IGFBP-5 PCR was performed by using human placenta CDNA (Marathon-Ready™ cDNA; Clontech) as a template, oligo DNA consisting of the base sequence of SEQ ID NO: 25 (having the restriction enzyme XbaI recognition sequence added to the 5′ terminus of the base sequence of the IGFBP-5 ORF of GenBank Accession No. M62782) and oligo DNA consisting of the base sequence of SEQ ID NO: 26 (having the restriction enzyme BamHI recognition sequence added to the 3′ terminus of the base sequence of the IGFBP-5 ORF of GenBank Accession No. M62782) as primers, and LAtaqDNA polymerase (Takara Shuzo). The PCR was carried out by performing a reaction at 94° C. for 2 minutes, repeating a cycle consisting of reactions at 98° C. for 10 seconds, at 60° C. for 20 seconds, and at 72° C. for 1 minute 40 times, and performing a reaction at 72° C. for 7 minutes. The resulting DNA fragment of approximately 0.8 kbp was subcloned into plasmid PCRII (Invitrogen). The base sequence was analyzed using a DNA sequencer (ABI3700 DNA Sequencer; Applied Biosystems) by a dideoxy terminator method to designate plasmid pCRII-IGFBP5. The plasmid PCRII-IGFBP5 was digested with restriction enzymes XbaI and BamHI, and the resulting DNA fragment of approximately 0.8 kbp was inserted between the XbaI site and BamHI site of the plasmid pCEPdE2-FLAG to construct plasmid pCEPdE2-IGFBP5-FLAG to express a IGFBP-5-FLAG protein having the FLAG tag of SEQ ID NO: 12 added to the C-terminus of the full-length IGFBP-5 protein (272 amino acids: SWISS PROT Accession No. P24593).

The procedure described in Example 8(1) was repeated, except for using the plasmid pCEPdE2-IGFBP5-FLAG instead of the expression plasmid pCEPdE2-MD8S-FLAG, to prepare recombinant IGFBP-5.

(2) Confirmation of Activity of Digesting Recombinant IGFBP-5 by MD8S

The MD8S enzyme solution obtained in Example 8(1) was reacted with recombinant IGFBP-5 obtained in Example 9(1) in a 50 mmol/L tris-HCl (pH7.4) buffer containing 50 mmol/L NaCl, 2 mmol/L CaCl2, 20 μg/mL bovine serum albumin (BSA), and 0.1% CHAPS at 37° C. overnight. In this connection, concentrations of the MD8S protein and recombinant IGFBP-5 in the reaction solution were 1.5 μg/mL and 10 μg/mL, respectively.

Using an aliquot of the reaction solution, SDS-PAGE was carried out, and then a transfer to a PVDF membrane and blocking was carried out. Recombinant IGFBP-5 was detected by reacting a biotinylated M2 antibody (Sigma) as the first antibody, followed by a horseradish peroxidase-labeled streptavidin (Amersham) as the second antibody, and by using an ECL Western Blotting Detecting System (Amersham Pharmacia).

It was confirmed that recombinant IGFBP-5, which was detected in the control without the MD8S enzyme solution, was made to disappear by adding the MD8S enzyme solution. It was also confirmed from the result that the MD8S protein exhibits an activity of digesting IGFBP-5.

Example 10 Screening of MD8S Inhibitor

Substances inhibiting the activity of digesting IGFBP-5 by the MD8S protein can be screened by the reaction system utilizing western blotting performed in Example 9(2). In this Example, the procedure described in Example 9(2) was repeated, except that various compounds having a hydroxamic acid scaffold as a compound to be tested were added to the reaction system containing the MD8S enzyme solution and recombinant IGFBP-5, to measure an inhibitory intensity of the activity of digesting IGFBP-5.

To calculate the intensity of the inhibition activity (IC₅₀), the degree of the inhibition activity in each concentration of the compounds to be tested was examined by performing image processing of the image on the film obtained by western blotting, using a scanner (ES-2200; Epson).

The criterion for screening substances inhibiting the activity of digesting IGFBP-5 was 10 μmol/L or less in the intensity of the inhibition activity (IC₅₀). N^(α)-[(3-carboxy-4-methylthio-2-propoxymethyl)butyryl]-N,O-dimethylthyrosineamide (WO93/09090; hereinafter referred to as compound A) was selected by this screening system. The intensity of the inhibition activity (IC₅₀) of the compound A was 3.3 μmol/L.

In this connection, the compound A can be synthesized by the method described in Example 5 of WO93/09090.

As a sample of screening, the result when using the compound A as a compound to be tested is shown in FIG. 3.

In FIG. 3, lane 1 shows the result when incubating only recombinant IGFBP-5, and lane 2 shows the result when incubating recombinant IGFBP-5 and the MD8S enzyme solution. Lanes 3 to 7 show the results when incubating recombinant IGFBP-5 and the MD8S enzyme solution in the presence of the compound A. Concentrations of the compound A in lanes 3 to 7 are 10 μmol/L, 1 μmol/L, 100 nmol/L, 10 nmol/L, and 1 nmol/L, respectively. The arrow indicates the position of IGFBP-5.

Example 11 Cloning of Base Sequence of 5′ Upstream of Human MD8 Gene ORF

PCR was performed by using human genome (Genomic DNA; Clontech) as a template, oligo DNAs consisting of the base sequence of SEQ ID NO: 21 or SEQ ID NO: 22 as primers, and DNA polymerase (Pyrobest DNA polymerase™; Takara Shuzo). The PCR was carried out by performing a reaction at 97° C. for 3 minutes, repeating a cycle consisting of reactions at 97° C. for 30 seconds, at 60° C. for 30 seconds, and at 72° C. for 2 minutes 40 times, and performing a reaction at 72° C. for 7 minutes. The resulting fragment of approximately 2 kbp consisting of the base sequence of SEQ ID NO: 20 was subcloned into a cloning vector (pCR4Blunt-TOPO;Invitrogen). The resulting subclone was treated with BamHI and HindIII, and the obtained fragment consisting of the base sequence of the 34th to 2014th bases in the base sequence of SEQ ID NO: 20 was cloned into a vector for a luciferase assay system (PicaGene Vector 2 basic vector; Toyo Ink MFG) which had been previously treated with BglII and HindIII, to obtain pGV-B2-ADAM8pro2k.

Example 12 Analysis of DNA Sequence of Human MD8 Promoter Region

The plasmid pGV-B2-ADAM8pro2k obtained in Example 11 was introduced into HEK293-EBNA cells (Invitrogen) cultured in a Dulbecco's modified Eagle's medium (DMEM) containing 10% fetal bovine serum, 100 μg/mL penicillin, 100 μg/mL streptomycin, and 250 μg/mL G418 (Nakarai Tesque) using a transfection reagent (FuGene-6; Nippon Roche). A luciferase activity after culturing for 36 or 48 hours under conventional culture conditions was measured with a commercially available measuring kit (PicaGene coloring kit; Toyo Ink MFG). In this connection, the measured values were compensated with the values of a β-gal activity expressed by a β-gal expression plasmid (pCH110; Amersham Pharmacia Biotech) which was co-introduced. The activity of β-gal was measured by a commercially available measuring kit (Galacto-Light Plus kit; Roche). As a result, an increased activity of luciferase, which was not detected in the original plasmid pGV-B2, was clearly observed (FIG. 4). This result shows that a promoter activity exists in the DNA fragment.

Referential Example 1 Measurement of Amount of MD8 Gene Expressed in Normal Mice and Diabetes Model Mice

Genes of which increased amounts were expressed in diabetes model mice were examined in a preliminary experiment using a gene chip. As a result, it was found that the increased gene of GenBank Accession No. X13335 was expressed. The following experiment was performed to confirm whether or not an amount of expression was actually increased in the diabetes model mice.

In this Referential Example, an amount of mRNA expression of GenBank Accession No. X13335 in epididymal fat of two diabetes model mice KKAy/Ta (Iwatsuka et al., Endocrinol. Japon., 17, 23-35, 1970) and C57BL/KsJ-db/db (Kaku et al., Diabetologia, 32, 636-643, 1989) was measured by a real time PCR method using a sequence detector (ABI PRISM-7700 Sequence Detector; Applied Biosystems), and compared to those of normal mice C57BL/6J and C57BL/KsJ-+m/+m.

(1) Extirpation of Mouse Tissue

Male C57BL/6J, KKAy/Ta, C57BL/KsJ-+m/+m, and C57BL/KsJ-db/db mice (eight mice per each) were purchased from CLEA JAPAN.

C57BL/6J mice were bred collectively with normal diet until 12 weeks old. KKAy/Ta mice were bred separately with a high calorie diet (CMF; Oriental Yeast Co., Ltd.) until 12 weeks old. C57BL/KsJ-+m/+m mice and C57BL/KsJ-db/db mice were bred collectively with normal diet until 12 weeks old.

It was confirmed that KKAy/Ta mice and C57BL/KsJ-db/db mice exhibited hyperglycemia and a high weight in comparison with normal mice (KKAy/Ta mice: blood glucose level=447.1±4.2 mg/dL, weight=45.9±0.6 g; C57BL/KsJ-db/db mice: blood glucose level=423.7±14.1 mg/dL, weight=48.6±0.5 g). These four kinds of mice were anesthetized with diethyl ether to extirpate epididymal fat. Each epididymal fat was quickly frozen with liquid nitrogen and kept at −80° C.

(2) Extraction of Total RNA

Each tissue obtained in Reference Example 1(1) was cracked by a frozen cell crasher (CRYO-PRESS CP-100; MICROTEC NITION). An RNA extraction reagent (ISOGEN; Nippon Gene) was added and the mixture was homogenized by a homogenizer (ULTRA-TURRAX T-8; IKA LABORTECHNIK). RNA was extracted from each sample in accordance with a protocol of the RNA extraction reagent (ISOGEN). The extract was treated with DNase (Nippon Gene) to digest contaminated DNA. Phenol/chloroform treatment and ethanol precipitation were performed. An RNA concentration was determined by measuring absorbance at 260 nm and 280 nm with a spectrometer (U-2000; Hitachi). RNA was diluted with water to 10 ng/μL, and kept at −20° C.

(3) Preparation of Primers and TaqMan™ Probe

A TaqMan™ probe, a 5′-primer, and a 3′-primer used in a reverse transcriptase-polymerase chain reaction (RT-PCR) were designed by searching appropriate sites using an analysis software (Primer Express; Applied Biosystems) on the basis of the sequence of the gene registered as Accession No. X13335 in the GenBank database. More particularly, the DNA consisting of the base sequence of SEQ ID NO: 3 and the DNA consisting of the base sequence of SEQ ID NO: 4 were used as the 5′-primer and 3′-primer, respectively, and the DNA consisting of the base sequence of SEQ ID NO: 5 was used as the TaqMan™ probe.

The 5′-primer and 3′-primer were synthesized by GENSET. The TaqMan™ probe wherein the 5′ terminus was labeled with a fluorescent dye FAM (6-carboxy-fluorescein) and the 3′ terminus was labeled with a fluorescent dye TAMRA (6-carboxy-tetramethyl-rhodamine) was prepared by Applied Biosystems.

(4) Measurement of Amount of mRNA Expression

An expression level of mRNA contained in the total RNA derived from epididymal fat and amplified by the primers, that is, which was considered as X13335, was determined by a sequence detector (ABI PRISM™ 7700 Sequence Detector; Applied Biosystems). According to this detection system, the time course of amounts of DNA strands amplified in each step of RT-PCR can be monitored by detecting a fluorescent signal, and the amount of mRNA expression can be quantified on the basis of the cycle number of PCR over a certain fluorescent strength.

A RT-PCR solution was prepared using a commercially available kit (TaqMan EZ RT-PCR Core Reagents; Applied Biosystems) in accordance with a protocol thereof. The RT-PCR was carried out by performing an RT reaction consisting of reactions at 55° C. for 50 minutes, at 60° C. for 10 minutes, and at 95° C. for 2 minutes and then repeating a PCR reaction consisting of reactions at 95° C. for 15 seconds and at 58° C. for 1.5 minutes 40 times. Aliquots (4 ng, 20 ng, 100 ng, and 500 ng per tube) of the total RNA prepared from epididymal fat of the KKAy/Ta mouse were added to tubes, and then RT-PCR was carried out together with samples to determine a standard line. The amounts of gene expression were compensated with those of 18S rRNA contained in the samples.

As a result, with respect to the mRNA considered as X13335, the amount of expression in the diabetes model KKAy/Ta mice was increased by approximately 10-fold in comparison with that in the normal C57BL/6J mice, and the amount of expression in the diabetes model C57BL/KsJ-db/db mice was increased by approximately 110-fold in comparison with that in the normal C57BL/KsJ-m+/m+mice as a control.

From the results, it is considered that the expression of the X13335 gene is increased in diabetes models.

INDUSTRIAL APPLICABILITY

According to the screening tool or screening method of the present invention, a therapeutic agent for diabetes, particularly an agent for alleviating insulin resistance, can be screened.

The novel polypeptide of the present invention exhibits an activity of inhibiting glucose uptake into an adipocyte by an insulin stimulation, and thus can be used for the screening tool or screening method of the present invention.

The polynucleotide, vector, and transformant of the present invention are useful in manufacturing the polypeptide of the present invention.

The promoter of the present invention can also be used for the screening tool or screening method of the present invention. The transformant of the present invention comprising the polynucleotide or promoter of the present invention can be used for the screening tool or screening method of the present invention.

The probe of the present invention can be used for analyzing an amount of a polynucleotide encoding the polypeptide of the present invention. Diabetes can be diagnosed by an increase in the amount of the polynucleotide expressed as an indicator.

FREE TEXT IN SEQUENCE LISTING

Features of “Artificial Sequence” are described in the numeric identifier <223> in the Sequence Listing.

More particularly, each of the base sequences of SEQ ID NOS: 8, 9, 11, 18, 19, and 22-26 is an artificially synthesized primer sequence.

The amino acid sequence of SEQ ID NO: 12 is a FLAG tag amino acid sequence.

The symbol “Xaa” in the amino acid sequence of SEQ ID NO: 15 means an arbitrary amino acid.

The amino acid sequence of SEQ ID NO: 20 is a sequence containing a promoter sequence of human MD8 gene.

Although the present invention has been described with reference to specific embodiments, various changes and modifications obvious to those skilled in the art are possible without departing from the scope of the appended claims. 

1. A screening tool for a therapeutic agent for diabetes, wherein the tool is (1) a polypeptide consisting of the amino acid sequence of SEQ ID NO: 2 or SEQ ID NO: 14, (2) a polypeptide exhibiting an activity of inhibiting glucose uptake into an adipocyte by an insulin stimulation, and comprising an amino acid sequence in which 1 to 10 amino acids are deleted, substituted, and/or inserted in the amino acid sequence of SEQ ID NO: 2 or SEQ ID NO: 14, (3) a polypeptide exhibiting an activity of inhibiting glucose uptake into an adipocyte by an insulin stimulation, and comprising the amino acid sequence of SEQ ID NO: 2 or SEQ ID NO: 14, or (4) a polypeptide exhibiting an activity of inhibiting glucose uptake into an adipocyte by an insulin stimulation, and consisting of an amino acid sequence having an 80% or more homology with that of SEQ ID NO: 2 or SEQ ID NO:
 14. 2. The screening tool for a therapeutic agent for diabetes according to claim 1, wherein the tool is (1) a polypeptide consisting of the amino acid sequence of SEQ ID NO: 2 or SEQ ID NO:
 14. 3. A screening tool for a therapeutic agent for diabetes, wherein the tool is a cell expressing the polypeptide according to claim 1 or
 2. 4. The screening tool for a therapeutic agent for diabetes according to claim 3, wherein the cell is a transformant.
 5. A screening tool for a therapeutic agent for diabetes, wherein the tool is (1) a polynucleotide consisting of the base sequence consisting of the 34th to 2014th bases in the base sequence of SEQ ID NO: 20, (2) a polynucleotide exhibiting a promoter activity of the polypeptide according to claim 1 or 2, and comprising a base sequence in which one or more bases are substituted, deleted, and/or inserted at 1 to 10 positions in the base sequence consisting of the 34th to 2014th bases in the base sequence of SEQ ID NO: 20, (3) a polynucleotide exhibiting a promoter activity of the polypeptide according to claim 1 or 2, and comprising at least a part of the base sequence consisting of the 34th to 2014th bases in the base sequence of SEQ ID NO: 20, or (4) a polynucleotide exhibiting a promoter activity of the polypeptide according to claim 1 or 2, and hybridizing under stringent conditions to a polynucleotide consisting of the base sequence consisting of the 34th to 2014th bases in the base sequence of SEQ ID NO:
 20. 6. The screening tool for a therapeutic agent for diabetes according to claim 5, wherein the polypeptide exhibits a promoter activity of the polypeptide according to claim 1 or 2, and comprises the base sequence consisting of the 34th to 2014th bases in the base sequence of SEQ ID NO:
 20. 7. A screening tool for a therapeutic agent for diabetes, wherein the tool is a cell comprising the polynucleotide according to claim 5 or
 6. 8. The screening tool for a therapeutic agent for diabetes according to claim 7, wherein the cell is a transformant.
 9. The screening tool according to any one of claims 1 to 8, wherein the therapeutic agent for diabetes is an agent for alleviating insulin resistance.
 10. A method for analyzing whether or not a substance to be tested is an inhibitor of the polypeptide according to claim 1 or 2, comprising the steps of: bringing a cell expressing the polypeptide according to claim 1 or 2 into contact with the substance to be tested, and analyzing an amount of glucose uptake by an insulin stimulation.
 11. A method for screening an inhibitor of the polypeptide according to claim 1 or 2, comprising the steps of: analyzing a substance to be tested by the method according to claim 10, and selecting an inhibitor.
 12. A method for screening a therapeutic agent for diabetes, comprising the steps of: analyzing a substance to be tested by the method according to claim 10, and selecting an inhibitor.
 13. A method for analyzing whether or not a substance to be tested inhibits a promoter activity of the polynucleotide according to claim 5 or 6, comprising the steps of: (1) bringing the cell according to claim 7 or 8 into contact with the substance to be tested, and (2) analyzing the promoter activity.
 14. A method for screening a substance which inhibits an expression of the polypeptide according to claim 1 or 2, comprising the steps of: analyzing a substance to be tested by the method according to claim 13, and selecting a substance which inhibits the promoter activity.
 15. A method for screening a therapeutic agent for diabetes, comprising the steps of: analyzing a substance to be tested by the method according to claim 13, and selecting a substance which inhibits the promoter activity.
 16. A process for manufacturing a pharmaceutical composition for treating diabetes, comprising the steps of: analyzing a substance to be tested by the method according to claim 10 or 13, and preparing a medicament containing the substance.
 17. A polypeptide exhibiting an activity of inhibiting glucose uptake into an adipocyte by an insulin stimulation, and comprising the amino acid sequence of SEQ ID NO:
 2. 18. A polypeptide consisting of the amino acid sequence of SEQ ID NO:
 2. 19. (1) A polynucleotide consisting of the base sequence consisting of the 34th to 2014th bases in the base sequence of SEQ ID NO: 20, (2) a polynucleotide exhibiting a promoter activity of the polypeptide according to claim 1 or 2, and comprising a base sequence in which one or more bases are substituted, deleted, and/or inserted at 1 to 10 positions in the base sequence consisting of the 34th to 2014th bases in the base sequence of SEQ ID NO: 20, (3) a polynucleotide exhibiting a promoter activity of the polypeptide according to claim 1 or 2, and comprising at least a part of the base sequence consisting of the 34th to 2014th bases in the base sequence of SEQ ID NO: 20, or (4) a polynucleotide exhibiting a promoter activity of the polypeptide according to claim 1 or 2, and hybridizing under stringent conditions to a polynucleotide consisting of the base sequence consisting of the 34th to 2014th bases in the base sequence of SEQ ID NO:
 20. 20. The polynucleotide according to claim 19, exhibiting a promoter activity of the polypeptide according to claim 1 or 2, and comprising the base sequence consisting of the 34th to 2014th bases in the base sequence of SEQ ID NO:
 20. 21. A transformant comprising the polynucleotide according to claim 19 or
 20. 22. A probe which hybridizes to a polynucleotide encoding the polypeptide according to claim 17 or 18 under stringent conditions. 